Method and device for wireless signal transmission or reception in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system and, specifically, to a method comprising the steps of: repeatedly transmitting a PUSCH; and repeatedly receiving the PDSCH in a DL duration immediately following after repeated transmission of the PDSCH, wherein when a terminal operates in an in-band mode, each PDSCH is received from an OFDM symbol subsequent to a k-th OFDM symbol in each corresponding time unit within the DL duration (k&gt;1), and in the case where the terminal operates in a guard-band mode or a stand-alone mode, signal reception is skipped at a starting portion of the DL duration when the PDSCH is repeatedly received.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/KR2018/009187, filed on Aug. 10, 2018, which claims the benefit ofKorean Application No. 10-2018-0056995, filed on May 18, 2018, KoreanApplication No. 10-2018-0053607, filed on May 10, 2018, KoreanApplication No. 10-2018-0050204, filed on Apr. 30, 2018, U.S.Provisional Application No. 62/662,204, filed on Apr. 24, 2018, U.S.Provisional Application No. 62/591,137, filed on Nov. 27, 2017, U.S.Provisional Application No. 62/586,208, filed on Nov. 15, 2017, and U.S.Provisional Application No. 62/543,928, filed on Aug. 10, 2017. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting/receivinga wireless signal. The wireless communication system includes anarrowband Internet of things (NB-IoT)-based wireless communicationsystem.

BACKGROUND

Wireless communication systems have been widely deployed to providevarious types of communication services such as voice or data. Ingeneral, a wireless communication system is a multiple access systemthat supports communication of multiple users by sharing availablesystem resources (a bandwidth, transmission power, etc.) among them. Forexample, multiple access systems include a code division multiple access(CDMA) system, a frequency division multiple access (FDMA) system, atime division multiple access (TDMA) system, an orthogonal frequencydivision multiple access (OFDMA) system, and a single carrier frequencydivision multiple access (SC-FDMA) system.

SUMMARY

An aspect of the present disclosure is to provide a method and apparatusfor efficiently transmitting and receiving a wireless signal in awireless communication.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

In an aspect of the present disclosure, a method of receiving a signalby a user equipment (UE) in a wireless communication system includesrepeatedly transmitting a physical uplink shared channel (PUSCH) andrepeatedly receiving a physical downlink shared channel (PDSCH) in adownlink period successive to the repeated transmissions of the PUSCH.When the UE operates in an in-band mode, reception of each PDSCH startsin an orthogonal frequency division multiplexing (OFDM) symbol after ak^(th) (k>1) OFDM symbol in a time unit related to the PDSCH in the DLperiod, and when the UE operates in a guard-band or stand-alone mode, asignal reception is skipped at the start of the DL period during therepeated receptions of the PDSCH.

In another aspect of the present disclosure, a UE in a wirelesscommunication system includes a radio frequency (RF) module and aprocessor. The processor is configured to repeatedly transmit a PUSCH,and repeatedly receive a PDSCH in a downlink period successive to therepeated transmissions of the PUSCH. When the UE operates in an in-bandmode, reception of each PDSCH starts in an OFDM symbol after a k^(th)(k>1) OFDM symbol in a time unit related to the PDSCH in the DL period,and when the UE operates in a guard-band or stand-alone mode, a signalreception is skipped at the start of the DL period during the repeatedreceptions of the PDSCH.

The UE may include a narrowband Internet of things (NB-IoT) UE.

When the UE operates in the guard-band or stand-alone mode, the signalreception may be skipped in at least part of a first OFDM symbol of afirst time unit in the DL period during the repeated receptions of thePDSCH. Herein, a signal reception may start in a first OFDM symbol ofeach of second and subsequent successive time units in the DL periodduring the repeated receptions of the PDSCH.

The repeated transmissions of the PUSCH and the repeated receptions ofthe PDSCH may be performed in time division multiplexing (TDM) in thesame carrier.

The PUSCH may include a narrowband PUSCH (NPUSCH), the PDSCH may includea narrowband PDSCH (NPDSCH), and a subcarrier spacing used fortransmission of the NPDSCH may be 15 kHz.

The wireless communication system may include a 3^(rd) party partnershipproject (3GPP)-based wireless communication system.

According to the present disclosure, wireless signal transmission andreception can be efficiently performed in a wireless communicationsystem.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain the principle of thedisclosure.

FIG. 1 is a diagram illustrating physical channels used in a 3^(rd)generation partnership project (3GPP) long term evolution (-advanced)(LTE(-A)) as an exemplary wireless communication system and a signaltransmission method using the same.

FIG. 2 is a diagram illustrating a radio frame structure.

FIG. 3 is a diagram illustrating a resource grid of a downlink slot.

FIG. 4 is a diagram illustrating a downlink (DL) subframe structure.

FIG. 5 is a diagram illustrating the structure of an uplink (UL)subframe used in LTE(-A).

FIG. 6 is a diagram illustrating a self-contained subframe structure.

FIG. 7 is a diagram illustrating a frame structure defined for 3GPP newradio access technology (NR).

FIG. 8 is a diagram illustrating arrangement of an in-band anchorcarrier for an LTE bandwidth of 10 MHz.

FIG. 9 is a diagram illustrating positions where narrowband Internet ofthings (NB-IoT) physical DL channels/signals are transmitted in afrequency division duplex (FDD) LTE system.

FIG. 10 is a diagram illustrating resource allocation for an NB-IoTsignal and an LTE signal in an in-band mode.

FIG. 11 is a diagram illustrating multi-carrier scheduling.

FIGS. 12 to 15 are diagrams illustrating signal transmission andreception according to the present disclosure.

FIG. 16 is a block diagram illustrating a base station (BS) and a userequipment (UE) applicable to the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure are applicable to a variety ofwireless access technologies such as code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) evolves from 3GPP LTE. While the following description is given,centering on 3GPP LTE/LTE-A for clarity, this is purely exemplary andthus should not be construed as limiting the present disclosure.

In a wireless communication system, a user equipment (UE) receivesinformation through downlink (DL) from a base station (BS) and transmitinformation to the BS through uplink (UL). The information transmittedand received by the BS and the UE includes data and various controlinformation and includes various physical channels according totype/usage of the information transmitted and received by the UE and theBS.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

When powered on or when a UE initially enters a cell, the UE performsinitial cell search involving synchronization with a BS in step S101.For initial cell search, the UE synchronizes with the BS and acquireinformation such as a cell Identifier (ID) by receiving a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the BS. Then the UE may receive broadcast information fromthe cell on a physical broadcast channel (PBCH). In the meantime, the UEmay check a downlink channel status by receiving a downlink referencesignal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Control information transmitted from the UE tothe BS is referred to as uplink control information (UCI). The UCIincludes hybrid automatic repeat and requestacknowledgement/negative-acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includes achannel quality indicator (CQI), a precoding matrix indicator (PMI), arank indicator (RI), etc. While the UCI is transmitted on a PUCCH ingeneral, the UCI may be transmitted on a PUSCH when control informationand traffic data need to be simultaneously transmitted. In addition, theUCI may be aperiodically transmitted through a PUSCH according torequest/command of a network.

FIG. 2 illustrates a radio frame structure. Uplink/downlink data packettransmission is performed on a subframe-by-subframe basis. A subframe isdefined as a predetermined time interval including a plurality ofsymbols. 3GPP LTE supports a type-1 radio frame structure applicable tofrequency division duplex (FDD) and a type-2 radio frame structureapplicable to time division duplex (TDD).

FIG. 2(a) illustrates a type-1 radio frame structure. A downlinksubframe includes 10 subframes each of which includes 2 slots in thetime domain. A time for transmitting a subframe is defined as atransmission time interval (TTI). For example, each subframe has aduration of 1 ms and each slot has a duration of 0.5 ms. A slot includesa plurality of OFDM symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. Since downlink usesOFDM in 3GPP LTE, an OFDM symbol represents a symbol period. The OFDMsymbol may be called an SC-FDMA symbol or symbol period. An RB as aresource allocation unit may include a plurality of consecutivesubcarriers in one slot.

The number of OFDM symbols included in one slot may depend on cyclicprefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2(b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 4(5) normalsubframes and 10 special subframes. The normal subframes are used foruplink or downlink according to UL-DL configuration. A subframe iscomposed of 2 slots.

Table 1 shows subframe configurations in a radio frame according toUL-DL configurations.

TABLE 1 Uplink- Downlink- downlink to-Uplink config- Switch pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 msD S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D DD D 6 5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes DwPTS(Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink PilotTimeSlot). DwPTS is used for initial cell search, synchronization orchannel estimation in a UE and UpPTS is used for channel estimation in aBS and uplink transmission synchronization in a UE. The GP eliminates ULinterference caused by multi-path delay of a DL signal between a UL anda DL.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 3 illustrates a resource grid of a downlink slot.

Referring to FIG. 3, a downlink slot includes a plurality of OFDMsymbols in the time domain. While one downlink slot may include 7 OFDMsymbols and one resource block (RB) may include 12 subcarriers in thefrequency domain in the figure, the present disclosure is not limitedthereto. Each element on the resource grid is referred to as a resourceelement (RE). One RB includes 12×7 REs. The number NRB of RBs includedin the downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

FIG. 4 illustrates a downlink subframe structure.

Referring to FIG. 4, a maximum of three (four) OFDM symbols located in afront portion of a first slot within a subframe correspond to a controlregion to which a control channel is allocated. The remaining OFDMsymbols correspond to a data region to which a physical downlink sharedchancel (PDSCH) is allocated. A basic resource unit of the data regionis an RB. Examples of downlink control channels used in LTE include aphysical control format indicator channel (PCFICH), a physical downlinkcontrol channel (PDCCH), a physical hybrid ARQ indicator channel(PHICH), etc. The PCFICH is transmitted at a first OFDM symbol of asubframe and carries information regarding the number of OFDM symbolsused for transmission of control channels within the subframe. The PHICHis a response of uplink transmission and carries a HARQ acknowledgment(ACK)/negative-acknowledgment (NACK) signal. Control informationtransmitted through the PDCCH is referred to as downlink controlinformation (DCI). The DCI includes uplink or downlink schedulinginformation or an uplink transmit power control command for an arbitraryUE group.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). Formats 0, 3, 3A and 4 for uplinkand formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink are definedas DCI formats. Information field type, the number of informationfields, the number of bits of each information field, etc. depend on DICformat. For example, the DCI formats selectively include informationsuch as hopping flag, RB assignment, MCS (Modulation Coding Scheme), RV(Redundancy Version), NDI (New Data Indicator), TPC (Transmit PowerControl), HARQ process number, PMI (Precoding Matrix Indicator)confirmation as necessary. Accordingly, the size of control informationmatched to a DCI format depends on the DCI format. An arbitrary DCIformat may be used to transmit two or more types of control information.For example, DIC formats 0/1A is used to carry DCI format 0 or DICformat 1, which are discriminated from each other using a flag field.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

The PDCCH carries a message known as DCI which includes resourceassignment information and other control information for a UE or UEgroup. In general, a plurality of PDCCHs can be transmitted in asubframe. Each PDCCH is transmitted using one or more CCEs. Each CCEcorresponds to 9 sets of 4 REs. The 4 REs are referred to as an REG. 4QPSK symbols are mapped to one REG. REs allocated to a reference signalare not included in an REG, and thus the total number of REGs in OFDMsymbols depends on presence or absence of a cell-specific referencesignal. The concept of REG (i.e. group based mapping, each groupincluding 4 REs) is used for other downlink control channels (PCFICH andPHICH). That is, REG is used as a basic resource unit of a controlregion. 4 PDCCH formats are supported as shown in Table 2.

TABLE 2 PDCCH Number of Number of Number of format CCEs (n) REGs PDCCHbits 0 1 9 72 1 2 8 144 2 4 36 288 3 5 72 576

CCEs are sequentially numbered. To simplify a decoding process,transmission of a PDCCH having a format including n CCEs can be startedusing as many CCEs as a multiple of n. The number of CCEs used totransmit a specific PDCCH is determined by a BS according to channelcondition. For example, if a PDCCH is for a UE having a high-qualitydownlink channel (e.g. a channel close to the BS), only one CCE can beused for PDCCH transmission. However, for a UE having a poor channel(e.g. a channel close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channelcondition.

LTE defines CCE positions in a limited set in which PDCCHs can bepositioned for each UE. CCE positions in a limited set that the UE needsto monitor in order to detect the PDCCH allocated thereto may bereferred to as a search space (SS). In LTE, the SS has a size dependingon PDCCH format. A UE-specific search space (USS) and a common searchspace (CSS) are separately defined. The USS is set per UE and the rangeof the CSS is signaled to all UEs. The USS and the CSS may overlap for agiven UE. In the case of a considerably small SS with respect to aspecific UE, when some CCEs positions are allocated in the SS, remainingCCEs are not present. Accordingly, the BS may not find CCE resources onwhich PDCCHs will be transmitted to available UEs within givensubframes. To minimize the possibility that this blocking continues tothe next subframe, a UE-specific hopping sequence is applied to thestarting point of the USS.

Table 3 shows sizes of the CSS and USS.

TABLE 3 Number of Number of candidates candidates PDCCH Number of incommon in dedicated format CCEs (n) search space search space 0 1 — 6 12 — 6 2 4 4 2 3 8 2 2

To control computational load of blind decoding based on the number ofblind decoding processes to an appropriate level, the UE is not requiredto simultaneously search for all defined DCI formats. In general, the UEsearches for formats 0 and 1A at all times in the USS. Formats 0 and 1Ahave the same size and are discriminated from each other by a flag in amessage. The UE may need to receive an additional format (e.g. format 1,1B or 2 according to PDSCH transmission mode set by a BS). The UEsearches for formats 1A and 1C in the CSS. Furthermore, the UE may beset to search for format 3 or 3A. Formats 3 and 3A have the same size asthat of formats 0 and 1A and may be discriminated from each other byscrambling CRC with different (common) identifiers rather than aUE-specific identifier. PDSCH transmission schemes and informationcontent of DCI formats according to transmission mode (TM) are arrangedbelow.

Transmission Mode (TM)

-   -   Transmission mode 1: Transmission from a single base station        antenna port    -   Transmission mode 2: Transmit diversity    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO (Multiple Input Multiple        Output)    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Single-antenna port (port 5) transmission    -   Transmission mode 8: Double layer transmission (ports 7 and 8)        or single-antenna port (port 7 or 8) transmission    -   Transmission mode 9: Transmission through up to 8 layers (ports        7 to 14) or single-antenna port (port 7 or 8) transmission

DCI Format

-   -   Format 0: Resource grants for PUSCH transmission    -   Format 1: Resource assignments for single codeword PDSCH        transmission (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mod 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/i-bit power adjustments

FIG. 5 illustrates a structure of an uplink subframe used in LTE(-A).

Referring to FIG. 5, a subframe 500 is composed of two 0.5 ms slots 501.Assuming a length of a normal cyclic prefix (CP), each slot is composedof 7 symbols 502 and one symbol corresponds to one SC-FDMA symbol. Aresource block (RB) 503 is a resource allocation unit corresponding to12 subcarriers in the frequency domain and one slot in the time domain.The structure of the uplink subframe of LTE(-A) is largely divided intoa data region 504 and a control region 505. A data region refers to acommunication resource used for transmission of data such as voice, apacket, etc. transmitted to each UE and includes a physical uplinkshared channel (PUSCH). A control region refers to a communicationresource for transmission of an uplink control signal, for example,downlink channel quality report from each UE, reception ACK/NACK for adownlink signal, uplink scheduling request, etc. and includes a physicaluplink control channel (PUCCH). A sounding reference signal (SRS) istransmitted through an SC-FDMA symbol that is lastly positioned in thetime axis in one subframe. SRSs of a plurality of UEs, which aretransmitted to the last SC-FDMAs of the same subframe, can bedifferentiated according to frequency positions/sequences. The SRS isused to transmit an uplink channel state to an eNB and is periodicallytransmitted according to a subframe period/offset set by a higher layer(e.g., RRC layer) or aperiodically transmitted at the request of theeNB.

To minimize data transmission latency, a self-contained subframe isconsidered in the next-generation radio access technology (RAT). FIG. 6illustrates an exemplary self-contained subframe structure. In FIG. 6,the hatched area represents a DL control region, and the black arearepresents a UL control region. The area having no marks may be used foreither DL data transmission or UL data transmission. In this structure,DL transmission and UL transmission are sequentially performed in onesubframe to transmit DL data and receive a UL ACK/NACK for the DL datain the subframe. As a result, the resulting reduction of a time taken toretransmit data when a data transmission error occurs may lead tominimization of the latency of a final data transmission.

At least the following four subframe types may be considered asexemplary self-contained subframe types. Periods are enumerated in timeorder.

-   -   DL control period+DL data period+guard period (GP)+UL control        period    -   DL control period+DL data period    -   DL control period+GP+UL data period+UL control period    -   DL control period+GP+UL data period

A PDFICH, a PHICH, and a PDCCH may be transmitted in the DL controlperiod, and a PDSCH may be transmitted in the DL data period. A PUCCHmay be transmitted in the UL control period, and a PUSCH may betransmitted in the UL data period. The GP provides a time gap forswitching from a transmission mode to a reception mode or from thereception mode to the transmission mode at an eNB and a UE. Some OFDMsymbol(s) at a DL-to-UL switching time may be configured as the GP.

In the environment of the 3GPP NR system, different OFDM numerologies,for example, different subcarrier spacings (SCSs) and hence differentOFDM symbol (OS) durations may be configured between a plurality ofcells aggregated for one UE. Accordingly, the (absolute time) durationof a time resource (e.g., SF, slot or TTI) (referred to as a time unit(TU) for convenience) including the same number of symbols may be setdifferently for the aggregated cells. Herein, the term symbol may coverOFDM symbol and SC-FDMA symbol.

FIG. 7 illustrates a frame structure for 3GPP NR. In 3GPP NR, one radioframe includes 10 subframes each being 1 ms in duration, like a radioframe in LTE/LTE-A (see FIG. 2). One subframe includes one or more slotsand the length of a slot varies with an SCS. 3GPP NR supports SCSs of 15KHz, 30 KHz, 60 KHz, 120 KHz, and 240 KHz. A slot corresponds to a TTIof FIG. 6.

As noted from Table 4, the number of symbols per slot, the number ofslots per frame, and the number of slots per subframe vary according toan SCS.

TABLE 4 Number of Number of Number of symbols slots per slots per SCS(15*2{circumflex over ( )}u) per slot frame subframe 15 KHz (u = 0) 1410 1 30 KHz (u = 1) 14 20 2 60 KHz (u = 2) 14 40 4 120 KHz (u = 3)  1480 8 240 KHz (u = 4)  14 160 16

A description will be given of narrowband Internet of things (NB-IoT).While NB-IoT is described based on the 3GPP LTE standards forconvenience, the following description is also applicable to the 3GPP NRstandards. For this purpose, some technical configurations may bereplaced with other ones in interpretation (e.g., LTE band→NR band andsubframe→slot).

NB-IoT supports three operation modes: in-band mode, guard-band mode,and stand-alone mode. The same requirements apply to each mode.

(1) In-band mode: a part of the resources of the LTE band are allocatedto NB-IoT.

(2) Guard-band mode: a guard frequency band of the LTE band is used, andan NB-IoT carrier is arranged as close as possible to an edge subcarrierof the LTE band.

(3) Stand-alone mode: some carriers in the GSM band are allocated toNB-IoT.

An NB-IoT UE searches for an anchor carrier in units of 100 kHz, forinitial synchronization, and the center frequency of the anchor carriershould be located within +7.5 kHz from a 100-kHz channel raster in thein-band and guard-band. Further, the center 6 physical resource blocks(PRBs) of the LTE PRBs are not allocated to NB-IoT. Therefore, theanchor carrier may be located only in a specific PRB.

FIG. 8 is a diagram illustrating arrangement of an in-band anchorcarrier in an LTE bandwidth of 10 MHz.

Referring to FIG. 8, a direct current (DC) subcarrier is located on achannel raster. Since the center frequency spacing between adjacent PRBsis 180 kHz, the center frequencies of PRBs 4, 9, 14, 19, 30, 35, 40 and45 are located at ±2.5 kHz from the channel raster. When the bandwidthis 20 MHz, the center frequency of a PRB suitable for transmission onthe anchor carrier is located at ±2.5 kHz from the channel raster, andwhen the bandwidth is 3 MHz, 5 MHz, or 15 MHz, the center frequency of aPRB suitable for transmission on the anchor carrier is located at ±7.5kHz from the channel raster.

In the guard-band mode, given bandwidths of 10 MHz and 20 MHz, thecenter frequency of a PRB immediately adjacent to an edge PRB of the LTEsystem is located at ±2.5 kHz from the channel raster. Further, givenbandwidths of 3 MHz, 5 MHz, and 15 MHz, a guard frequency bandcorresponding to three subcarriers from an edge PRB is used, and thusthe center frequency of the anchor carrier may be located at ±7.5 kHzfrom the channel raster.

In the stand-alone mode, an anchor carrier is aligned with the 100-kHzchannel raster, and all GSM carriers including the DC carrier may beavailable as NB-IoT anchor carriers.

Further, NB-IoT may support multiple carriers, and a combination ofin-band and in-band, a combination of in-band and guard-band, acombination of guard-band and guard-band, and a combination ofstand-alone and stand-alone are available.

NB-IoT DL uses OFDMA with a 15-kHz SCS. OFDMA provides orthogonalitybetween subcarriers, so that the NB-IoT system and the LTE system maycoexist smoothly.

For NB-IoT DL, physical channels such as a narrowband physical broadcastchannel (NPBCH), a narrowband physical downlink shared channel (NPDSCH),and a narrowband physical downlink control channel (NPDCCH) may beprovided, and physical signals such as a narrowband primarysynchronization signal (NPSS), a narrowband primary synchronizationsignal (NSSS), and a narrowband reference signal (NRS) are provided.

The NPBCH delivers minimum system information required for an NB-IoT UEto access the system, a master information block-narrowband (MIB-NB) tothe NB-IoT UE. The NPBCH may be transmitted repeatedly eight times intotal for coverage enhancement. The transport block size (TBS) of theMIB-NB is 34 bits and updated every TTI of 640 ms. The MIB-NB includesinformation about an operation mode, a system frame number (SFN), ahyper-SFN, the number of cell-specific reference signal (CRS) ports, anda channel raster offset.

The NPSS is composed of a Zadoff-Chu (ZC) sequence of length 11 and aroot index of 5. The NPSS may be generated by the following equation.

$\begin{matrix}{{{d_{l}(n)} = {{S(l)} \cdot e^{{- j}\; \frac{\pi \; {un}{({n + 1})}}{11}}}},{n = 0},1,\ldots \mspace{11mu},10} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

S(l) for symbol index l may be defined as illustrated in Table 5.

TABLE 5 Cyclic prefix length S(3), . . . , S(13) Normal 1 1 1 1 −1 −1 11 1 −1 1

The NSSS is composed of a combination of a ZC sequence of length 131 anda binary scrambling sequence such as a Hadamard sequence. The NSSSindicates a PCID to NB-IoT UEs within the cell by the combination ofsequences.

The NSSS may be generated by following equation.

$\begin{matrix}{{d(n)} = {{b_{q}(m)}e^{{- j}\; 2\; {\pi\theta}_{f}n}e^{{- j}\; \frac{\pi \; {{un}^{\prime}{({n^{\prime} + 1})}}}{131}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Variables applied to Equation 2 may be defined as follows.

$\begin{matrix}{{{n = 0},1,\ldots \mspace{11mu},131}{n^{\prime} = {n\; {mod}\; 131}}{m = {{n{mod}}\; 128}}{u = {{N_{ID}^{Ncell}{mod}\; 126} + 3}}{q = \left\lfloor \frac{N_{ID}^{Ncell}}{126} \right\rfloor}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

A binary sequence b_(q)(m) may be defined as illustrated in Table 6, andb₀(m) to b₃(m) represent columns 1, 32, 64, and 128 of a Hadamard matrixof order 128. A cyclic shift θ_(f) for a frame number n may be definedby Equation 4 below.

TABLE 6 q b_(q)(0), . . . b_(q)(127) 0 [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1] 1 [1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 11 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1−1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 11 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −11 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1] 2 [1 −1 −1 1 −1 1 1 −1 −1 1 1−1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 11 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 − 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1−1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −11 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1−1 1] 3 [1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1−1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 11 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −11 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1−1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1]

$\begin{matrix}{\theta_{f} = {\frac{33}{132}\left( {\eta_{f}\text{/}2} \right){{mod}4}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In Equation 4, nf represents a radio frame number and mod represents amodulo function.

The NRS, which is a reference signal for channel estimation required fordemodulation of a DL physical channel, is generated in the same manneras in LTE. However, the NRS uses a narrowband-physical cell ID (NB-PCID)(or NCell ID or NB-IoT BS ID) as an initial value for initialization.The NRS is transmitted through one or two antenna ports (p=2000 and2001).

The NPDCCH has the same transmission antenna configuration as the NPBCH,and delivers DCI. The NPDCCH supports three types of DCI formats. DCIformat N0 includes scheduling information about a narrowband physicaluplink shared channel (NPUSCH), and DCI formats N1 and N2 includesNPDSCH scheduling information. The NPDCCH may be transmitted repeatedlyup to 2048 times, for coverage enhancement.

The NPDSCH is used to transmit data of a transport channel such as aDL-SCH or a paging channel (PCH). The NPDSCH has a maximum TBS of 680bits and may be transmitted repeatedly up to 2048 times, for coverageenhancement.

FIG. 9 is a diagram illustrating positions where narrowband NB-IoTphysical DL channels/signals are transmitted in an FDD LTE system.

Referring to FIG. 9, the NPBCH is transmitted in the first subframe ofeach radio frame, the NPSS is transmitted in the sixth subframe of eachradio frame, and the NSSS is transmitted in the last subframe of eacheven-numbered frame. An NB-IoT UE acquires frequency synchronization,symbol synchronization, and frame synchronization and searches 504 PCIDs(i.e., BS IDs) by synchronization signals (NPSS and NSSS). The LTSsynchronization signals are transmitted in 6 PRBs, whereas the NB-IoTsynchronization signals are transmitted in one PRB.

In NB-IoT, UL physical channels include a narrowband physical randomaccess channel (NPRACH) and an NPUSCH, and support single-tonetransmission and multi-tone transmission. Multi-tone transmission issupported only for an SCS of 15 kHz, and single-tone transmission issupported for SCSs of 3.5 kHz and 15 kHz. On UL, when the SCS is 15 kHz,orthogonality with the LTE system is maintained, thereby providingoptimum performance. However, the 3.75-kHz SCS may destroy theorthogonality, resulting in performance degradation due to interference.

An NPRACH preamble includes four symbol groups, each including a CP andfive (SC-FDMA) symbols. The NPRACH supports only single-tonetransmission with the 3.75-kHz SCS and provides CPs of 66.7 μs and266.67 μs in length to support different cell radiuses. Each symbolgroup is subjected to frequency hopping in the following hoppingpattern. Subcarriers carrying the first symbol group are determinedpseudo-randomly. The second symbol group hops by one subcarrier, thethird symbol group hops by six subcarriers, and the fourth symbol grouphops by one subcarrier. In the case of repeated transmissions, thefrequency hopping procedure is repeatedly applied. To enhance coverage,the NPRACH preamble may be repeatedly transmitted up to 128 times.

The NPUSCH supports two formats. NPUSCH format 1 is used for UL-SCHtransmission and has a maximum TBS of 1000 bits. NPUSCH format 2 is usedfor UCI transmission such as HARQ-ACK signaling. NPUSCH format 1supports single-tone transmission and multi-tone transmission, whereasNPUSCH format 2 supports only single-tone transmission. In single-tonetransmission, p/2-binary phase shift keying (BPSK) and p/4-quadraturephase shift keying (QPSK) may be used to reduce a peak-to-average powerratio (PAPR).

In the stand-alone and guard-band modes, all resources of one PRB may beallocated to NB-IoT. However, there is a constraint on resource mappingin the in-band mode, for co-existence with a legacy LTE signal. Forexample, resources (OFDM symbols 0 to 2 in each subframe) classified asa region allocated for LTE control channels may not be allocated to theNPSS and NSSS, and NPSS and NSSS symbols mapped to LTE CRS REs arepunctured.

FIG. 10 is a diagram illustrating resource allocation to an NB-IoTsignal and an LTE signal in the in-band mode. Referring to FIG. 10, forease of implementation, the NPSS and NSSS are not transmitted in OFDMsymbols corresponding to the control region of the legacy LTE system(the first three OFDM symbols of a subframe) regardless of an operationmode. NPSS/NSS REs colliding with LTE CRS REs in physical resources arepunctured, for mapping without affecting the legacy LTE system.

After the cell search, the NB-IoT UE demodulates the NPBCH withoutsystem information except for a PCID. Therefore, NPBCH symbols may notbe mapped to the LTE control channel allocation region. Moreover, sincethe NB-IoT UE assumes four LTE antenna ports (e.g., p=0, 1, 2, and 3)and two NB-IoT antenna ports (e.g., p=2000 and 2001) in the situationwithout system information, the NB-IoT UE may not allocate the NPBCH toCRS REs and NRS REs. Therefore, the NPBCH is rate-matched according toavailable resources.

After demodulating the NPBCH, the NB-IoT UE may acquire informationabout the number of CRS antenna ports. However, the NB-IoT UE still maynot acquire information about the LTE control channel allocation region.Therefore, the NPDSCH carrying system information block type 1 (SIB1)data is not mapped to resources classified as the LTE control channelallocation region.

However, unlike the NPBCH, REs which are not allocated to the LTE CRSmay be allocated to the NPDSCH. Since the NB-IoT UE has acquired allinformation related to resource mapping after receiving SIB1, an eNB maymap the NPDSCH (except for the case where SIB1 is transmitted) and theNPDCCH to available resources based on LTE control channel informationand the number of CRS antenna ports.

FIG. 11 is a diagram illustrating an exemplary operation when multiplecarriers are configured in FDD NB-IoT. In FDD NB-IoT, a DL/UL anchorcarrier is basically configured, and a DL (and UL) non-anchor carriermay be additionally configured. RRCConnectionReconfiguration may includeinformation about the non-anchor carrier. When the DL non-anchor carrieris configured, a UE receives data only in the DL non-anchor carrier. Incontrast, synchronization signals (NPSS and NSSS), a broadcast signal(MIB and SIB), and a paging signal are provided only in the anchorcarrier. When the DL non-anchor carrier is configured, the UE listens toonly the DL non-anchor carrier while the UE is in an RRC_CONNECTEDstate. Similarly, when the UL non-anchor carrier is configured, the UEtransmits data only in the UL non-anchor carrier, not being allowed totransmit data simultaneously in the UL non-anchor carrier and the ULanchor carrier. When the UE transitions to an RRC IDLE state, the UEreturns to the anchor carrier.

In the illustrated case of FIG. 11, UE1 is configured only with anchorcarriers, UE2 is configured additionally with a DL/UL non-anchorcarrier, and UE3 is configured additionally with a DL non-anchorcarrier. Accordingly, each UE transmits and receives data in thefollowing carriers.

-   -   UE1: data reception (DL anchor carrier) and data transmission        (UL anchor carrier)    -   UE2: data reception (DL non-anchor carrier) and data        transmission (UL non-anchor carrier)    -   UE3: data reception (DL non-anchor carrier) and data        transmission (UL anchor carrier)

The NB-IoT UE is not capable of simultaneous transmission and reception,and a transmission/reception operation is limited to one band.Therefore, even though multiple carriers are configured, the UE requiresonly one transmission/reception chain in a 180-kHz band.

Embodiment: Inter-Cell Interference Mitigation for NB-IoT

When the NB-IoT system operates in TDD, there is a need for a method ofeffectively using DL subframes and UL subframes during UL repeatedtransmissions and DL repeated transmissions. A method of reducing powerconsumption of a UE and effectively managing resources is also required.For this purpose, the present disclosure largely proposes (1) a UL/DLinterlaced scheduling method, (2) a DL early termination method, (3) aUL early termination method, and (4) a switching time securing method.

The UL/DL interlaced scheduling method proposed in the presentdisclosure may be applied to a system supporting multiple repetitions ofDL and UL transmissions/receptions. Particularly, the UL/DL interlacedscheduling method may be applied effectively, when DL and UL alternateduring repeated transmissions/receptions. While the present disclosureis described in the context of an NB-IoT system conforming to 3GPP LTERel-13 and Rel-14, for the convenience of description, the descriptionis also applicable to a system conforming to a subsequent release, asystem requiring repeated transmissions as in eMTC, and other generalsystems. Further, although the present disclosure is effectivelyapplicable to a case in which the amounts of DL and UL resources aredifferent according to a UL/DL configuration as in TDD, the presentdisclosure may also be used, when DL resources and UL resources are notenough for repeated transmissions in a system operating in any otherduplex mode.

In the following description, the NPDCCH may be replaced by the PDCCH orDL (physical) control channel, and the NPDSCH may be replaced by thePDSCH, DL (physical) shared channel, or DL (physical) data channel. TheNPUSCH may be replaced by the PUSCH, UL (physical) shared channel, or UL(physical) data channel.

(1) UL/DL Interlaced Scheduling Method

In a TDD system, DL and UL alternate with each other every predeterminedperiod in the time domain (e.g., every 5 ms or 10 ms in LTE). When a DLreception is not allowed before a UL transmission is completed, DLresources which appear every predetermined period may be wasted in asystem characterized by repeated transmissions in one HARQ process, likeNB-IoT. Resources may also be wasted when a UL transmission is notallowed before a DL reception is completed. To avert the problem, UL/DLinterlaced scheduling methods are proposed, in which UL and DL alternatewith each other, for transmission/reception.

[Method #1: Single DCI-Based UL/DL Scheduling]

To transmit UL data and receive DL data, a UE needs to receive a ULgrant and a DL grant in DL resources (e.g., a DL subframe or slot). Asystem suffering from shortage of DL resources like a TDD systemrequires a method of including both a UL grant and a DL grant in oneDCI, instead of independently transmitting the UL grant and the DLgrant. For this purpose, a single DCI-based UL/DL scheduling method isproposed, and the DCI may need an additional field indicating “ULgrant”, “DL grant”, or “UL/DL grant”. The following may be considered.

-   -   A “DCI for simultaneous UL and DL scheduling” (hereinafter,        referred to as a DL/UL joint DCI) and a “DCI for separate UL and        DL scheduling” may be defined in different formats (e.g.,        payload sizes). The UE may not attempt to simultaneously detect        the two DCI formats at a specific time.    -   When the “DCI for simultaneous UL and DL scheduling” and the        “DCI for separate UL and DL scheduling” are defined in the same        payload size, 2-bit flags identifying a format may be included        in the DCIs.    -   A 1-bit flag may be defined as a “flag for differentiation        between format N0 and format N1”. The other 1-bit flag may be        used to indicate a format for simultaneous UL and DL scheduling.        DCI format N0 includes NPUSCH scheduling information, and DCI        format N1 includes NPDSCH scheduling information. DCI format N0        and DCI format N1 are of the same payload size.    -   Values 0 to 3 represented in the 2 bits may indicate “DL        scheduling”, “UL scheduling”, “UL/DL scheduling”, and “DL/UL        scheduling”, respectively. UL/DL and DL/UL may be used to        indicate which one of UL and DL immediately follows the DCI.    -   When UL and DL are simultaneously scheduled, a UL scheduling        delay (i.e., a DCI-to-NPUSCH delay) and a DL ACK/NACK delay        (i.e., an NPDSCH-to-ACK/NACK delay) may be derived from common        delay information/value. That is, both the UL scheduling delay        and the DL ACK/NACK delay may be set using one delay value,        thereby effectively reducing a DCI payload size.    -   (Opt. 1) The single DCI (DL/UL joint DCI) may indicate only an        NPUSCH scheduling delay (NPUSCH transmission timing), and an        ACK/NACK for an NPDSCH may always be piggybacked to a        corresponding NPUSCH. Whether to piggyback an ACK/NACK may be        determined differently according to the number of remaining        subframes (i.e., a remaining repetition number) of NPUSCH format        1 on the time axis after the NPDSCH is decoded. For example,        when the remaining repetition number is not enough for repeated        transmissions of the ACK/NACK, some of the ACK/NACK repeated        transmissions may be piggybacked to the remaining NPUSCH format        1, while the remaining ACK/NACK repeated transmissions may be        performed in NPUSCH format 2. When the remaining repetition        number of NPUSCH format 1 is enough for repeated transmissions        of the ACK/NACK, the ACK/NACK may be piggybacked to NPUSCH        format 1, while NPUSCH format 1 may be transmitted without        ACK/NACK piggyback during the remaining repeated transmission        period of NPUSCH format 1.    -   (Opt. 2) The single DCI (DL/UL joint DCI) may indicate only a        single delay value, and the delay value may be commonly applied        to the ACK/NACK delay (NPDSCH-to-ACK/NACK delay) and the UL        scheduling delay (DCI-to-NPUSCH delay). The common application        of the single delay value may mean that (1) the same delay        information is derived from the single delay value or (2) each        piece of delay information is derived independently from the        single delay value. In the case of (2), different pieces of        delay information may be derived from the single delay value.

FIGS. 12, 13 and 14 illustrate exemplary signal transmissions accordingto Opt. 2. In FIGS. 12, 13 and 14, an SCH is an NPUSCH or NPDSCHaccording to resources (i.e., UL or DL resources), and a U/D grant(i.e., DL/UL joint DCI) schedules UL and DL by one NPDCCH. In FIGS. 12,13 and 14, UL and DL may represent a UL carrier and a DL carrier,respectively, or UL resources (e.g., a UL subframe or slot) and DLresources (e.g., a DL subframe or slot) of the same carrier. Further,the U/D grant may imply that UL scheduling information and DL schedulinginformation are delivered on an NPDCCH at time points which are notoverlapped. k0 may be indicated by the U/D grant and used as both of theNPDSCH-to-ACK/NACK delay and the DCI-to-NPUSCH delay. A/N representsACK/NACK information for DL-SCH data (e.g., TB). DL-SCH data may betransmitted on an NPDSCH, and UL-SCH data may be transmitted on anNPUSCH. Different hatching on UL and DL implies changing of a scramblingsequence and/or a redundancy version during repeated transmissions of aphysical channel.

Referring to FIGS. 12, 13 and 14, an ACK/NACK for a DL-SCH (e.g.,NPDSCH) may be piggybacked to NPUSCH format 1 (FIGS. 12 and 13) ortransmitted separately (FIG. 14) according to the presence or absence ofa subframe of NPUSCH format 1 after an NPDSCH-to-ACK/NACK delay (e.g.,k0) from a reception time of the last subframe of the DL-SCH. FIG. 12illustrates a case in which UL-SCH (e.g., NPUSCH) subframes and DL-SCHsubframes end at similar time points, and FIG. 13 illustrates a case inwhich UL-SCH subframes exist after the last subframe of a DL-SCH. In theillustrated case of FIG. 13, a DL grant may be monitored duringtransmission of the UL-SCH subframes. FIG. 14 illustrates a case inwhich there are no UL-SCH subframes after the last subframe of a DL-SCH.

[Method #2: Separate DCI-Based Independent UL and DL Scheduling]

-   -   When the UE is repeatedly transmitting UL data (the UE is        repeatedly transmitting UL data in one UL HARQ process and all        UL HARQ processes of the UE have been scheduled), the UE may        monitor an NPDCCH in a DL subframe before the repeated        transmissions of the UL data are completed (see FIG. 13). When        all of the UL HARQ processes of the UE have been scheduled and        thus UL transmissions are in progress in the UL HARQ processes,        the UE may not expect new UL scheduling (during the UL        transmissions). Accordingly, when all of the UL HARQ processes        of the UE have been scheduled and thus UL transmissions are in        progress in the UL HARQ processes, with some of DL HARQ        processes not scheduled, the UE may expect that DCI of an NPDCCH        monitored additionally in a DL subframe period during the        repeated transmissions of UL data is for DL scheduling. The DCI        which is expected to be for DL scheduling may be in a DL compact        DCI format. After the repeated transmissions of UL data, the UE        may normally monitor a DL grant DCI format and a UL grant DCI        format.    -   The DL compact DCI format is a format with no possibility of        being interpreted as a UL grant. For example, the DL compact DCI        format may be DCI format N0/N1 without the “flag for        differentiation between format N0/format N1”. Conventionally,        DCI format N0 and DCI format N1 are of the same payload size and        distinguished from each other by a 1-bit flag for        differentiation between format N0 and format N1.    -   When the UE is repeatedly receiving DL data (the UE is        repeatedly receiving DL data in one DL HARQ process), the UE may        monitor an NPDCCH in a specific DL subframe before the repeated        receptions of the DL data are completed or when the repeated        receptions of the DL data are completed and an ACK/NACK is yet        to be reported. When all of the DL HARQ processes of the UE have        been scheduled and thus DL receptions are in progress in the DL        HARQ processes, the UE may not expect new DL scheduling (during        the DL receptions). Accordingly, when all of the DL HARQ        processes of the UE have been scheduled and thus DL receptions        are in progress in the DL HARQ processes, with some of UL HARQ        processes not scheduled, the UE may expect that DCI of an NPDCCH        monitored additionally (in a specific DL subframe period) is for        UL scheduling. The DCI which is expected to be for UL scheduling        may be in a UL compact DCI format. The UL compact DCI may be        used for UL early termination (e.g., refer to Methods #6, #7 and        #8). When the repeated receptions of DL data are completed and        an ACK/NACK for the DL data is reported, the UE may normally        monitor a DL grant DCI format and a UL grant DCI format.    -   The UL compact DCI format is a format with no possibility of        being interpreted as a DL grant. For example, the UL compact DCI        format may be DCI format N0/N1 without the “flag for        differentiation between format N0/format N1”.    -   The UL compact DCI format may be a format designed to request        reporting of an ACK/NACK for DL data which is being received.        Upon receipt of the UL compact DCI format, the UE may report an        ACK/NACK (or only when the ACK/NACK is an ACK) for DL data in        indicated UL resources (e.g., an NPUSCH) before completely        receiving the DL data as many times as a repetition number        initially set for the DL data.    -   When the UE is repeatedly transmitting UL data (the UE is        repeatedly transmitting UL data in one UL HARQ process and all        UL HARQ processes of the UE have been scheduled), the UE may not        monitor an NPDCCH in a DL subframe period (e.g., skip NPDCCH        monitoring) when all of the DL HARQ processes of the UE have        been scheduled or an ACK/NACK for DL data is yet to be reported.

[Method #3: Method of Configuring DCI Monitoring]

-   -   UL/DL interlaced scheduling is applicable only to a UE at or        above (or at or below) a specific coverage enhancement (CE)        level. Referring to 3GPP LTE Rel-14, a mobility management        entity (MME) may define up to three CE levels, that is, CE level        0 to CE level 2. A message is transmitted repeatedly based on a        CE level according to the location of a UE.    -   A UE below (or above) the specific CE level may not monitor an        NPDCCH (e.g., skip NPDCCH monitoring) before a scheduled UL or        DL HARQ process is completed.    -   However, a UE having two or more HARQ processes may monitor an        NDPCCH even before the scheduled UL or DL HARQ processes are        completed.    -   UL/DL interlaced scheduling is applicable only to an NPDCCH set        to a specific Rmax value or less (or the Rmax value or greater).        Rmax represents an NPDCCH repetition number.    -   In UL/DL interlaced scheduling, an NPUSCH and/or an NPDSCH may        be scheduled only with a specific repetition number or greater        (the specific repetition number or less).    -   Before as many NPUSCH transmissions as a configured repetition        number are completed, NPDCCH monitoring may be performed in a        specific DL subframe/slot period (e.g., see FIG. 13).    -   When the repeated NPUSCH transmissions take time longer than a        predetermined time, the UE may attempt to detect an NPDCCH for a        predetermined time in an NPDCCH monitoring carrier (see FIG.        11). The predetermined time may be a UL gap or a value allowed        for tracking DL synchronization.    -   A UL grant which has indicated the NPUSCH transmissions may        directly indicate a gap period for NPDCCH monitoring.

As described above, DL and UL subframes (slots) which alternatenon-continuously on the time axis may be used effectively in UL/DLinterlaced scheduling. However, UL/DL interlaced scheduling requiresadditional NPDCCH monitoring, resulting in consumption of more UE power.To mitigate this problem, the UE may expect UL/DL interlaced schedulingor perform additional NPDCCH monitoring, only under a specificcondition. For example, only when the number of DL subframes between ULrepeated transmissions is less than a specific value (or ratio) or isequal to or less than a maximum repetition number of the NPDCCH, the UEmay expect/perform additional NPDCCH monitoring. Alternatively, when arepetition number for an NPUSCH is greater than a specific value, the UEmay additionally monitor an NPDCCH in some time period, upon occurrenceof a condition for postponing NPUSCH transmissions by the time period.This may be configured in consideration of a UL/DL switching gap of theUE. Further, a UL grant which has scheduled the NPUSCH may explicitlyconfigure a specific time period during which an NPDCCH may be monitoredduring repeated NPUSCH transmissions.

(2) DL Early Termination Method

The measurement accuracy of an NB-IoT system operating in a narrowbandand supporting a large max coupling loss (MCL) is lower than that of asystem using a wideband. Therefore, an eNB may set an NPDSCH repetitionnumber to too large a value based on an inaccurate measurement receivedfrom a UE. In this case, the UE may succeed in decoding an NPDSCH beforereceiving the NPDSCH as many times as the configured repetition number.To overcome this resource waste, there is a need for a method ofreporting a DL ACK/NACK before repeated NPDSCH receptions are completed.Particularly when UL resources alternate with DL resources as in a TDDsystem, a method of fast reporting an ACK/NACK in UL resources existingbetween DL repeated receptions may be applied effectively.

[Method #4: Method of Configuring DL Early Termination]

-   -   When UL resources alternate with DL resources in the time        domain, an ACK may be reported fast in UL resources between DL        repeated receptions.    -   Before repeated receptions in a configured DL HARQ process are        completed, a DL decoding result may be reported on UL only when        the DL decoding result is an ACK.    -   A plurality of ACK/NACK reporting delays may be configured for a        scheduled DL HARQ process by a DL grant.    -   Only when an ACK is generated during repeated NPDSCH receptions,        the UE may report the ACK in ACK/NACK resources configured in UL        resources (e.g., a UL subframe or slot) corresponding to an        ACK/NACK reporting delay earlier than the longest ACK/NACK        reporting delay.    -   When the UE has not reported the ACK before the longest ACK/NACK        reporting delay, the UE may report the ACK or NACK in the last        of configured ACK/NACK resources (i.e., ACK/NACK resources        configured at the longest ACK/NACK reporting delay).    -   When the UE has reported the ACK before the longest ACK/NACK        reporting delay but has not received an indication indicating        transmission discontinuation for the corresponding DL HARQ        process explicitly/implicitly, the UE may report the ACK or NACK        in the last of the configured ACK/NACK resources.

For example, when scheduling an NPDSCH by a DL grant, the eNB mayconfigure a plurality of DL ACK/NACK reporting resources. Each of the DLACK/NACK reporting resources may correspond to an ACK/NACK reportingdelay. Let the plurality of DL ACK/NACK reporting resources be denotedsequentially by 1 to N (N>1). Then, ACK/NACK resource 1 to ACK/NACKresource N−1 may be used only when the decoding result of the NPDSCHbeing received is an ACK. When the UE has not reported an ACK inACK/NACK resource 1 to ACK/NACK resource N−1 or when the UE has reportedan ACK in ACK/NACK resource 1 to ACK/NACK resource N−1 but the eNB hasnot indicated discontinuation of a corresponding DL HARQ processexplicitly or implicitly, the UE may report an ACK or NACK in ACK/NACKresource N. ACK/NACK resource N corresponds to the longest ACK/NACKreporting delay.

-   -   Case in which an ACK occurs before DL repeated receptions are        completed and a UL data transmission has been scheduled.    -   When a transmission in NPUSCH format 1 is in progress along with        repeated NPDSCH receptions, upon generation of an ACK as an        NPDSCH decoding result, the UE may transmit the ACK in NPUSCH        format 2, discontinuing the transmission of NPUSCH format 1 for        a specific time period.    -   The ACK may be in NPUSCH format 1 which is being transmitted.        Data at the position of the ACK in NPUSCH format 1 may be        punctured. A NACK may not be piggybacked to NPUSCH format 1.

[Method #5: Method of Simultaneously Transmitting ACK/NACK and UL Data]

-   -   An ACK/NACK and UL data may be multiplexed (ACK/NACK piggyback).    -   When the number of tones in NPUSCH format 1 for UL data        transmission is less than the number of tones (12 tones) in one        RB, NPUSCH format 1 and NPUSCH format 2 for ACK/NACK reporting        may be multiplexed in FDM.    -   The ACK/NACK may be mapped to OFDM symbols at both sides of a        DMRS in NPUSCH format 1, and data of NPUSCH format 1 at both        sides of the DMRS may be punctured.    -   The ACK/NACK may be transmitted by skipping a part of repeated        transmissions of NPUSCH format 1.    -   When the number of tones in NPUSCH format 1 is less than the        number of tones in one RB, resources available for piggyback of        the ACK (or ACK/NACK) are multiplexed in FDM with data resources        to which the ACK (or ACK/NACK) is not piggybacked so that the        eNB may distinguish the ACK (or ACK/NACK) from data.

It may be allowed to transmit NPUSCH format 1 to which the ACK/NACK ispiggybacked with higher power than NPUSCH format 1 to which the ACK/NACKis not piggybacked.

-   -   The ACK/NACK and the UL data may be transmitted separately.    -   A DL grant-to-ACK/NACK delay and a UL grant-to-NPUSCH format 1        scheduling delay may be set to one value. After the scheduling        delay, repeated transmissions of NPUSCH format 2 for ACK/NACK        reporting may start, followed successively by a transmission of        NPUSCH format 1. That is, NPUSCH format 1 and NPUSCH format 2        for ACK/NACK reporting may be multiplexed in TDM.    -   The ACK/NACK may be transmitted in a special subframe.    -   A DL grant may configure a plurality of ACK/NACK reporting        delays for a corresponding DL HARQ process. Only when an ACK is        generated during repeated NPDSCH receptions, the UE may report        the ACK in ACK/NACK resources allocated for an ACK/NACK        reporting delay earlier than the longest ACK/NACK reporting        delay. When the UE has not reported an ACK before the longest        ACK/NACK reporting delay, the UE may always report an ACK or        NACK in the last of configured ACK/NACK resources (i.e.,        ACK/NACK resources configured in UL resources (e.g., subframe or        slot) corresponding to the longest ACK/NACK reporting delay).

(3) UL Early Termination Method

The measurement accuracy of an NB-IoT system operating in a narrowbandand supporting a large MCL is lower than that of a system using awideband. Therefore, the eNB may set an NPUSCH repetition number to toolarge a value based on an inaccurate measurement received from the UE.Therefore, the eNB may succeed in decoding an NPUSCH before receivingthe NPUSCH as many times as the configured repetition number. In thiscase, use of unnecessary UL resources may be reduced and unnecessarypower consumption of the UE may be prevented, by fast feeding back anACK for the UL data on DL.

[Method #6: Method of Configuring UL Early Termination]

-   -   Before repeated NPUSCH transmissions are completed, NPDCCH        monitoring may be performed in a DL subframe period.    -   An explicit ACK channel may be monitored. A NACK may not be        transmitted separately before the repeated NPUSCH transmissions        are completed.    -   An ACK report may be received implicitly by monitoring a UL        grant. For example, when a new UL grant is configured for a UL        HARQ process in which the transmissions are in progress, the UE        may interpret that an ACK has been received for the UL HARQ        process.    -   NPDCCH DCI that the UE monitors before as many NPUSCH        transmissions as an indicated repetition number are not        completed may be UL compact DCI designed for UL early        termination. For example, the UE may attempt blind decoding only        for the UL compact DCI designed for UL early termination. A        maximum repetition number for the UL compact DCI may be less        than a maximum repetition number for (normal) DCI for a UL        grant.    -   An ACK report may be received implicitly by monitoring a DL        grant. For example, upon receipt of a DL grant 1) before the UL        transmissions are completed or 2) when the UL transmissions have        been completed but ACK/NACK information for the corresponding UL        HARQ process has not been received, the UE may interpret that an        ACK has been received for the UL HARQ process for which the        transmissions are in progress.    -   When repeated NPUSCH transmissions do not satisfy a specific        condition, the UE may not attempt NPDCCH monitoring for UL early        termination. This is because monitoring an NPDCCH in a DL        subframe between repeated NPUSCH transmissions at all times at        the UE may cause unnecessary power consumption. Accordingly,        when there is a very low probability that an ACK results from        decoding the NPUSCH which is being repeatedly transmitted,        NPDCCH monitoring for UL early termination may be skipped. For        example, the specific condition is given as follows.    -   A predetermined ratio or more of as many repeated NPUSCH        transmissions as an NPUSCH repetition number indicated by a UL        grant have not been completed.    -   A DL subframe period available for NPDCCH monitoring between        repeated NPUSCH transmissions is shorter than a predetermined        value (i.e., the number of DL subframes available for an ACK        feedback for UL early termination is less than a predetermined        value).    -   The NUPUSCH repetition number indicated by the UL grant is less        than a specific value.    -   An NPDSCH is interlaced-scheduled and thus NPUSCH transmissions        and NPDSCH receptions are interlaced. That is, when UL data and        DL data are being transmitted and received through interlaced        scheduling, an NPDSCH reception may be performed with priority        over NPDCCH monitoring in a DL subframe period between repeated        NPUSCH transmissions.

[Method #7: Method of Monitoring Explicit ACK/NACK During ULTransmissions]

-   -   An ACK for a UL HARQ process may be transmitted in a DL subframe        apart from an NPUSCH transmission time by a predetermined time        interval. A NACK may not be transmitted separately. An ACK/NACK        channel monitored during repeated NPUSCH transmissions, for UL        early termination may be designed to be an explicit ACK channel        (synchronous ACK/NACK). The explicit ACK channel may be designed        to always carry an ACK report in DL resources/period placed in a        specific relationship with NPUSCH transmission resources. For        example, the specific relationship may be established between        resources (e.g., transmission time/frequency tones) of the        explicit ACK channel and the starting subframe (or slot) and/or        the positions/number of tones and/or a repetition number of        NPUSCH format 1 carrying data for a UL HARQ process, and the        resources for the explicit ACK channel may be reserved        accordingly. Therefore, the UE may monitor an ACK for the UL        HARQ process in specific preset DL resources during        transmissions of NPUSCH format 1. When the UE fails in detecting        the ACK, the UE may continue transmitting ongoing NPUSCH format        1.

[Method #8: Method of Monitoring Implicit ACK/NACK (DCI) During ULTransmissions]

-   -   When a new data indicator (NDI) for a UL HARQ process of NPUSCH        format 1 being transmitted is toggled and indicates an ACK        implicitly, it may be indicated separately whether a new data        transmission is to be skipped. According to the implicit        ACK/NACK method, toggling an NDI (UL grant) for a UL HARQ        process for which transmissions have been completed or are in        progress is interpreted as an ACK/NACK for UL data. When the NDI        for the UL HARQ process is toggled, the NDI may indicate/be        interpreted as transmission of new data in the UL HARQ process,        and when the NDI for the UL HARQ process is not toggled, the NDI        may indicate/be interpreted as retransmission or continuous        transmission in the UL HARQ process for which transmissions have        been completed or are in progress. When an ACK has been        generated for the UL HARQ process or a new data transmission in        the UL HARQ process is not needed, there is no way for UL early        termination or its effect may be mitigated. That is, because the        HARQ-ACK feedback is interpreted as an ACK, the UE may        discontinue data transmission in the UL HARQ process. However,        the UE should start a new transmission irrespective of whether        new transmission data exists. To avert this problem, a UL grant        may explicitly indicate whether a new data transmission is to be        skipped, along with an NDI for a UL HARQ process.    -   Even though an NDI for a UL HARQ process is toggled in a        received new UL grant before as many NPUSCH transmissions as an        NPUSCH repetition number indicated by a UL grant are completed,        a new data transmission in the UL HARQ process may be skipped.        For example, when an NDI for a UL HARQ process for which        transmissions are in progress is toggled in a new UL grant        before all of repeated NPUSCH transmissions indicated by a UL        grant are completed, the UE may discontinue an ongoing        transmission of NPUSCH format 1 without transmitting new data        for a time period corresponding to the remainder of a previously        configured NPUSCH format 1 repetition number.

(4) Method of Securing a Time Gap for Transceiver Switching (DL-to-ULSwitching and UL-to-DL Switching) Between UL and DL Interlaces

In general, a transceiver switching time for DL-to-UL switching andUL-to-DL switching is required. When the transceiver switching time isnot secured, a constraint may be imposed on use of the last period of apreceding (physical) channel and/or the starting period of a following(physical) channel in UL-to-DL or DL-to-UL interlacedtransmission/reception. To solve the problem, a method of securing atime gap is required. However, the method of securing a time gap may beapplied differently according to an operation mode or the like. Further,when a time (i.e., a time period in which a UE does not expect a DLsignal reception or is not allowed to transmit a UL signal) used tosecure a time gap corresponds to part of a TTI or a basic unit time(e.g., a subframe or slot) used to fully transmit one physical channel,various methods of configuring a channel of a time period in which atransmission is allowed or a reception may be expected within a basictime unit are available. For example, a signal in a time period used asa time gap may be ignored or a transmission/reception channel may berate-matched differently in consideration of a time gap.

[Method #9: Method of Securing a Time Gap for Transceiver Switching(DL-to-UL Switching and UL-to-DL Switching) Between UL and DLInterlaces]

-   -   Interlaced scheduling and transmission/reception of interlaced        channels may need a different time gap according to an operation        mode.    -   In-band operation mode.    -   There may be no need for an explicit time gap between an        NPDCCH/NPDSCH reception and an NPUSCH transmission. Therefore,        no time gap may be defined between an NPDCCH/NPDSCH reception        and an NPUSCH transmission. Instead, a ‘GP+UpPTS’ period        included a special subframe between a DL subframe and a UL        subframe may be used as a guard time for a time gap (see FIG.        2(b)). Alternatively, the DwPTS of a special subframe        immediately before the NPUSCH transmission may be configured        such that the UE is not allowed to receive an NPDCCH/NPDSCH in        the DwPTS. This may be different according to the length of the        DwPTS. Further, the non-received NPDCCH/NPDSCH in the DwPTS        period may not be counted in a total repetition number.    -   An explicit time gap may not be needed between an NPUSCH        transmission and an NPDCCH/NPDSCH reception. Therefore, no        explicit time gap may not be defined between an NPUSCH        transmission and an NPDCCH/NPDSCH reception. Instead, the        control area (see FIG. 4) of the first (1^(st)) DL subframe in        which the DL signal is received (immediately) after the UL        transmission may be used as a guard time for a time gap.        Information about the size (e.g., the number of symbols) of the        control area of the DL subframe may be transmitted in an NB-IoT        SIB. When the size of the control area of the first DL subframe        in which the DL signal is received (immediately) after the UL        transmission is not enough for accommodating the guard time, the        size of the control area of the first DL subframe may be set to        a value larger than the value set in the NB-IoT SIB. That is,        when a UL/DL interlacing operation is performed, the UE may        interpret the size of the control area of the first DL subframe        in which the DL signal is received (immediately) after the UL        transmission as different from (e.g., larger than) the value        broadcast in the SIB. However, the size of the control area in        the other DL subframes except for the first DL subframe may be        interpreted as equal to the value broadcast in the SIB.    -   Guard-band and stand-alone operation modes.    -   There may be no need for an explicit time gap between an        NPDCCH/NPDSCH reception and an NPUSCH transmission. Therefore,        no explicit time gap may be defined between an NPUSCH        transmission and an NPDCCH/NPDSCH reception. Instead, a        ‘GP+UpPTS’ period included in a special subframe between a DL        subframe and a UL subframe may be used as a guard time for a        time gap. Therefore, even when the UpPTS is available for the        NPUSCH transmission, the UpPTS of the special subframe following        the DL reception may not be used. That is, the UE may        determine/interpret differently whether to use the UpPTS of a        special subframe for an NPUSCH transmission, depending on        whether UL/DL interlacing is applied/performed. That is, when        UL/DL interlacing is applied/performed, even though the UpPTS is        available for the NPUSCH transmission, the UpPTS of the special        subframe following the DL reception may not be used. When UL/DL        interlacing is not applied/performed and the UpPTS is available        for the NPUSCH transmission, the UpPTS of the special subframe        following the DL reception may be used for the NPUSCH        transmission.    -   In another method, an explicit time gap may be defined between        an NPUSCH transmission and an NPDCCH/NPDSCH reception. For this        purpose, a specific subframe or slot may be allocated fully as a        guard time, or a virtual control area may be configured and used        as a guard time. When a specific subframe or slot is allocated        as a guard time, a constraint may be imposed on use of a        successive DL subframe (immediately) after a UL subframe        depending on whether UL/DL interlacing is applied/performed.        When a virtual control area is used as a guard time, the number        of OFDM symbols in the control area may be any non-zero value.        That is, although the number of symbols in a control area is        assumed to be zero in the guard-band and stand-alone modes, when        UL/DL interlacing is applied/performed, the UE may be configured        not to expect reception of a DL signal (e.g., NPDCCH/NPDSCH)        during the corresponding time period by setting the size of the        control area in the first (1^(st)) DL subframe or a successive        DL subframe (immediately) after a UL transmission (e.g., NPUSCH)        to a value larger than zero. Accordingly, the UE may skip the DL        signal (e.g., NPDCCH/NPDSCH) reception at the start of the first        (1^(st)) DL subframe (immediately) after the UL transmission        (e.g., NPUSCH). The guard time for switching may be understood        as an implicit gap in the sense that a specific number of        symbols (e.g., corresponding to a specific size of a control        area in the foregoing example) between an NPUSCH transmission        and an NPDCCH/NPDSCH reception are always not used. For example,        when the operation mode is the guard-band or stand-alone mode,        the number of symbols for transceiver switching may not be        signaled independently but assumed to be a specific value.        Therefore, the UE may skip a DL signal (e.g., NPDCCH/NPDSCH)        reception at the start of the first (1^(st)) DL subframe (or        successive DL subframe) (immediately) after a UL transmission        (e.g., NPUSCH).

FIG. 15 is a diagram illustrating exemplary DL signal receptionsaccording to the present disclosure.

Referring to FIG. 15, a UE (e.g., NB-IoT UE) may transmit a PUSCHrepeatedly in a UL period (or duration). The UL period may include aplurality of time units (e.g., TTIs, subframes, or slots), and eachPUSCH may be transmitted in a corresponding time unit of the UL period.The UE may then be scheduled to repeatedly receive a PDSCH in a DLperiod (or duration) immediately after the repeated PUSCH transmissions.The DL period may also include a plurality of time units (e.g., TTIs,subframes, or slots), and each PDSCH may be transmitted in acorresponding time unit of the DL period. When the UE operates in thein-band mode, the UE may start to receive each PDSCH in an OFDM symbolafter a k^(th) OFDM symbol in a corresponding time unit of the DLperiod. Herein, k is an integer larger than 1 and may be received insystem information (SI) (e.g., an NB-IoT SIB).

When the UE operates in the guard-band or stand-alone mode, the UE mayskip a signal reception (operation) at the start of the DL period duringrepeated PDSCH receptions. For example, for the first (1^(st)) PDSCH, asignal reception (operation) may be skipped in at least part of thefirst OFDM symbol of a corresponding time unit. Reception of each of thesecond and subsequent PDSCHs may start in the first (1^(st)) symbol of acorresponding time unit.

The repeated PUSCH transmissions and the repeated PDSCH receptions maybe performed in TDM in the same carrier. A UL/DL resource configurationfor the carrier may be indicated by a UL/DL configuration listed inTable 1. In NB-IoT, the PUSCH may include the NPUSCH, and the PDSCH mayinclude the NPDSCH. An SCS used for the (N)PDSCH transmissions may be 15kHz. Further, the wireless communication system may include a 3GPP-basedwireless communication system.

-   -   In the above methods, a guard time period (e.g., subframe, slot,        symbol(s), part of a symbol) for transceiver switching may be        punctured or rate-matched.    -   The punctured time period may be the first (1^(st)) symbol of        the UL period, the last symbol of the UL period, the first        symbol of the DL period, the last symbol of the DL period, or a        UL and DL combination of the above periods. The punctured time        period may vary depending on whether the punctured time period        includes an RS.    -   In the above methods, when the UE receives a DL signal (e.g.,        NPDCCH/NPDSCH) immediately after a UL transmission (e.g., an        NPUSCH transmission), the UE may not receive the DL signal        (i.e., the UE may skip the NPDCCH/NPDSCH reception) in the first        (1^(st)) OFDM symbol (i.e., the first OFDM symbol of a DL        subframe (immediately) after a UL subframe) (or at least part of        the first (1^(st)) OFDM symbol) of the DL period, although the        eNB actually transmits the first (1^(st)) OFDM symbol (i.e., the        first (1^(st)) OFDM symbol of the DL subframe). That is, the UE        may interpret the OFDM symbol as punctured. However, the eNB may        transmit the OFDM symbol without puncturing it to UEs for which        UL/DL interlacing is not performed, much transceiver switching        time is not required, or a sufficient transceiver switching time        is given by an offset as long as a timing advance (TA) of a UL        transmission channel. When a time gap is generated between a UL        transmission and a DL reception immediately after the UL        transmission due to a UL or DL invalid subframe, no transceiver        switching time may be needed. In this case, the UE may normally        receive the first (1st) OFDM symbol of the DL period (shortly        after the UL transmission).    -   When a guard time is included in subframes for which repeated        transmissions are configured, data of a transmission channel may        be rate-matched or punctured according to a repetition number        for the transmission channel in a transmission period except for        the guard time in the subframes. For example, when the        repetition number is less than a predetermined value, the data        may be rate-matched in consideration of resources (e.g., REs) of        the remaining time period except for the guard time. When the        repetition number is larger than the predetermined value, the        guard time may be punctured, while rate matching may not be        applied to the remaining time period except for the guard time.        Because the repetition number of the transmission channel is        large in a low signal-to-noise (SNR) environment, the same        mapping between repeated transmissions (i.e., mapping of the        same information to the same REs between repeated transmissions        by puncturing) may be more effective than a coding gain based on        rate-matching.    -   A time period used to secure a transceiver switching time and an        interlacing scheduling constraint or a transmission/reception        constraint may be different according to the operation mode of a        carrier. A time for frequency retuning may be different        according to the operation mode of the carrier used after the        frequency retuning. For example, in frequency retuning from a UL        carrier to a DL carrier, when the DL carrier is in the in-band        operation mode, a gap of 1 ms may not be needed. Even in this        case, the UE may not expect to receive some first (1^(st))        symbols of an NB-IoT channel (e.g., the first (1^(st)) OFDM        symbol after a CFI of a legacy LTE UE, configured for an NB-IoT        UE by system information) or part of the first (1^(st)) symbol,        within 1 ms. When the DL carrier is in the guard-band or        stand-along operation mode, the UE may not expect the NB-IoT        channel for the first 1 ms or the duration of a slot. That is, a        specific method of ensuring a frequency retuning time may be        different depending on whether a time period during which        reception of an NB-IoT channel/signal may not be expected is        included in the frequency retuning time.    -   A time period used to secure a transceiver switching time and an        interlacing scheduling constraint or a transmission/reception        constraint may be different depending on whether a carrier is an        anchor carrier or a non-anchor carrier. For example, in        frequency retuning from a UL carrier to a DL carrier, when the        DL carrier is a non-anchor carrier, a gap of 1 ms may not be        needed. Even in this case, the UE may not expect to receive some        first (1^(st)) symbols of an NB-IoT channel (e.g., the first        OFDM symbol after a CFI of a legacy LTE UE, configured for an        NB-IoT UE by system information) or part of the first (1^(st))        symbol, within 1 ms, thereby defining no explicit guard time.        When the DL carrier is an anchor carrier, an explicit guard time        may be defined such that the UE does not expect the NB-IoT        channel for the first 1 ms or the duration of a slot.    -   A time period used to secure a transceiver switching time and an        interlacing scheduling constraint or a transmission/reception        constraint may be different depending on whether a guard time        period required for UL-to-DL switching includes a valid or        invalid subframe.    -   A time period used to secure a transceiver switching time and an        interlacing scheduling constraint or a transmission/reception        constraint may be different depending on whether a TA is applied        to a UL channel transmitted by a UE in the UL period of a        UL-to-DL period. For example, when an NPRACH is transmitted, a        TA is not applied, thus imposing a constraint on use of a        following DL subframe, for a transceiver switching gap of the        UL-to-DL period. That is, it may be necessary to limit use of        some DL OFDM symbol or subframe (e.g., 1 ms) (by puncturing or        rate-matching). Further, a required DL restriction period may        vary according to an NPRACH format transmitted by the UE. For        example, the DL restriction period may be set to a different        value (e.g., a period subjected to puncturing or rate-matching)        depending on whether the NPRACH transmitted by the UE is based        on an NPDCCH order, transmitted in RRC_CONNECTED mode,        contention-based, or contention-free-based. It may be defined        that a UE receives a DL channel/signal following an NPUSCH        transmission to which a TA is applied. Obviously, a specific        condition for receiving a DL channel/signal may be defined        according to the above-described conditions (operation mode,        anchor/non-anchor carrier, and valid/invalid subframe).

It may be defined that Method #9 is not applied in a situation in whichMethod #10 is applied or npusch-AllSymbols and srs-SubframeConfig areconfigured to avoid an SRS transmission from a legacy LTE UE. Forexample, when a UE transmits a UL signal in a UL valid subframeimmediately before reception of a DL valid subframe and skipping oftransmission of (one or more) last symbols is indicated, Method #9 maynot be applied. Herein, a DL valid subframe refers to a subframeavailable for an NPDCCH or NPDSCH transmission, and a UL valid subframerefers to a subframe available for an NPUSCH transmission. Accordingly,for example, in the illustrated case of FIG. 15, when the UE transmitsan NPUSCH in a UL subframe immediately before a subframe carrying anNPDSCH (i.e., in a subframe in which a fourth NPUSCH transmission isperformed), skipping of transmission of (one or more) last symbols maybe indicated/configured. In the in-band operation mode, the UE operatesin the manner illustrated in FIG. 15. In the guard-band/stand-alongoperation mode, the UE does not skip a signal reception (operation) atthe start of the DL subframe immediately after the subframe carrying anNPUSCH. That is, the UE may start to receive the NPDSCH signal in thefirst (1^(st)) symbol of the DL subframe shortly after the subframecarrying the NPUSCH.

Method #10: Method of Securing a Time Gap for Transceiver Switching(DL-to-UL Switching and UL-to-DL Switching) and/or an RF Switching Gapby Using an SRS Period Configuration

In addition to a method of configuring an implicit time gap for atransceiver switching gap and an RF switching gap, a method of securinga switching gap by configuring an SRS transmission period may beavailable. In Method #9, a UE is not allowed to receive part of a DLsignal after switching and transition. In contrast, in the method ofsecuring a switching gap by using an SRS transmission period, a time gapis secured by allowing/configuring a UE not to transmit part of a ULsignal before switching.

Table 7 illustrates an example of configuring npusch-AllSymbols andsrs-SubframeConfig to avoid an SRS transmission from a legacy LTE UE.

TABLE 7 When higher layer parameter npusch-All Symbols is set to false,resource elements in SC-FDMA symbols overlapping with a symbolconfigured with SRS according to srs-SubframeConfig shall be counted inthe NPUSCH mapping but not used for transmission of the NPUSCH. Whenhigher layer parameter npusch-AllSymbols is set to true, all symbols aretransmitted

When npusch-AllSymbols is set to false, a UE does not use a specific ULsubframe/symbol period configured as SRS resources during an NPUSCHtransmission. srs-SubframeConfig indicates a subframe periodicity/offsetused to define a subframe set configured with an SRS transmission.Although the method described in Table 7 is intended to protect an SRStransmission of a legacy UE, the method may be used for another purpose,that is, for the purpose of using a switching time for an NB-IoT UE. Tothis end, the definition and value of srs-SubframeConfig may be changed.

In another example, it may be defined that a UL-to-DL switching gap issecured, for example, by using only npusch-AllSymbols or its similarinformation without directly using srs-SubframeConfig. For example, whennpusch-AllSymbols (or a similar parameter, that is, a parameterindicating non-transmission of the last symbol of an NPUSCH, the lastsymbol of a successive UL valid subframe, or the last symbol of a ULvalid subframe in a period in which the UL valid subframe is adjacent toa DL valid subframe) is set to false, this may indicate skipping oftransmission of the last symbol of the UL valid subframe. The proposedinterpretation/indication may be limited to the followings. Thefollowings may be combined.

-   -   The proposed interpretation/indication may be applied only to a        UE for which UL/DL interlacing is configured or performed. That        is, even when corresponding information is configured commonly        within a cell, only UEs configured to perform a UL/DL        interlacing operation may skip transmission of the corresponding        UL last symbol.    -   The proposed interpretation/indication may be applied only when        a UL valid subframe is adjacent to a DL valid subframe. That is,        only when there is no gap between a UL valid subframe and a DL        valid subframe, or the number of symbols in the control area of        a DL valid subframe after a UL valid subframe is ‘zero’ or less        than a specific value, UEs may skip transmission of the        corresponding last symbol. Even though a valid UL subframe and a        valid DL subframe are successive, when there is a period during        which a UE expects to perform no reception in the first        (adjacent) DL valid subframe shortly after a UL transmission        (and the size of the period is larger than a predetermined        value), the operation of skipping transmission of a last UL        symbol may not be performed. For example, when a gap of 1 ms or        longer is configured in an NPDCCH monitoring period after an        NPUSCH format 2 transmission, or there is a period in which a UE        is not allowed to receive a signal in a valid DL subframe        shortly after a UL transmission, the operation of skipping        transmission of a last UL symbol may not be performed.

The proposed interpretation/indication may be applied differentlyaccording to an NB-IoT operation mode. For example, because the controlarea of a subframe may be used for a UL-to-DL gap in the in-bandoperation mode, the operation of skipping transmission of a last ULsymbol may not be performed. Therefore, the operation of skippingtransmission of a last UL symbol may be performed only in theguard-band/stand-alone operation mode.

Further, when Method #9 is applied, Method #10 may not be configured orthe operation of Method #10 may be skipped.

The proposed Method #9 and Method #10 may be used to secure atransceiver switching gap and, when an NB-IoT/eMTC relay is introduced,to mitigate interference between links/channels of a BS and a relay, arelay and a UE, and a relay and a relay. That is, when a relaycommunicates with 1) a BS, 2) a UE serviced by the relay, or 3) a relayat the next hop, by time division, time gaps may be required among theperiods of 1), 2) and 3) and the proposed Method #9 and Method #10 maybe used to secure the time gaps.

The UL/DL interlaced scheduling method proposed in the presentdisclosure may correspond to a UE capability, for example, relate to thenumber of HARQ processes. That is, a UE supporting only single-HARQ maynot expect interlaced scheduling. However, a throughput may be moreimproved by interlaced scheduling than by 2-HARQ, according to a UL/DLconfiguration in a TDD system. Therefore, the UE supporting onlysingle-HARQ may also indicate support of interlaced scheduling by aseparate capability signal. Further, interlaced scheduling may besupported in a manner satisfying a specific method or a specificcondition in consideration of the complexity of a buffer/memory of theUE (when a soft buffer of a receiver and a soft-buffer of a transmitterare shared). Only when the specific method or the specific condition issatisfied, the eNB may perform interlaced scheduling. For example, theeNB may perform interlaced scheduling such that an NPDSCH to bescheduled for a UE and an NPUSCH to be scheduled on UL do not exceed aspecific memory size (e.g., a reference memory size set based on asingle-HARQ buffer or a reference memory size set based on a 2-HARQbuffer, in consideration of the HARQ process capability of the UE). Whenthe NPDSCH is scheduled earlier than the NPUSCH, and then the NPUSCH isscheduled in a situation in which an ACK/NACK for the NPDSCH has notbeen received or detected, an NPUSCH which may use only the remainingbuffer/memory space may be scheduled, on the assumption that thescheduled NPDSCH is all present in the buffer/memory of the UE. Herein,the reception soft buffer of the UE may calculate the number of bits inwhich an LLR is represented per information bit by using a specificvalue indicated by the eNB or defined in the standards. When the UEreceives interleaved scheduling that does not satisfy that, the whole orpart of the buffer may be overwritten with newly received or transmittedinformation, or belated received interleaved scheduling may be ignored.

FIG. 16 illustrates a BS and a UE of a wireless communication system,which are applicable to embodiments of the present disclosure.

Referring to FIG. 16, the wireless communication system includes a BS110 and a UE 120. When the wireless communication system includes arelay, the BS or UE may be replaced by the relay.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present disclosure. The memory114 is connected to the processor 112 and stores information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives an RF signal. The UE 120includes a processor 122, a memory 124 and an RF unit 126. The processor122 may be configured to implement the procedures and/or methodsproposed by the present disclosure. The memory 124 is connected to theprocessor 122 and stores information related to operations of theprocessor 122. The RF unit 126 is connected to the processor 122 andtransmits and/or receives an RF signal.

The embodiments of the present disclosure described hereinbelow arecombinations of elements and features of the present disclosure. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent disclosure may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent disclosure may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present disclosure or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present disclosure, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term‘UE’ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present disclosure may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present disclosure may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentdisclosure may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

The present disclosure is applicable to UEs, eNBs or other apparatusesof a wireless mobile communication system.

1. A method of receiving a signal by a user equipment (UE) in atime-domain duplexing (TDD)-based wireless communication system, themethod comprising: detecting a narrowband physical downlink controlchannel (NPDCCH); and based on the detection of the NPDCCH, receiving anarrowband physical downlink shared channel (NPDSCH) in a downlinksubframe on a carrier, wherein the downlink subframe immediately followsan uplink subframe, wherein, based on the carrier being in an in-bandmode, the NPDSCH is received starting from k^(th) (k>1) orthogonalfrequency division multiplexing (OFDM) symbol, without skipping any partof the NPDSCH, and wherein, based on the carrier being in a guard-bandor stand-alone mode, the NPDSCH is received, with skipping a startingpart of the NPDSCH.
 2. The method according to claim 1, wherein the UEincludes a narrowband Internet of things (NB-IoT) UE.
 3. The methodaccording to claim 1, wherein, based on the carrier being in theguard-band or stand-alone mode, the reception of the NPDSCH is skippedin at least part of 1^(st) OFDM symbol of the downlink subframe.
 4. Themethod according to claim 3, wherein, based on the carrier being in theguard-band or stand-alone mode, the NPDSCH is placed starting from PtOFDM symbol of the downlink subframe.
 5. The method according to claim1, wherein the NPDSCH is received, without skipping any part of theNPDSCH, further based on two hybrid automatic repeat request (HARQ)processes being configured.
 6. The method according to claim 1, whereina subcarrier spacing used for the NPDSCH is 15 kHz.
 7. The methodaccording to claim 1, wherein the wireless communication system includesa 3rd party partnership project (3GPP)-based wireless communicationsystem.
 8. A user equipment (UE) in a time-domain duplexing (TDD)-basedwireless communication system, the UE comprising: a radio frequency (RF)module; and a processor, wherein the processor is configured to detect anarrowband physical downlink control channel (NPDCCH), and, based on thedetection of the NPDCCH, receive a narrowband physical downlink sharedchannel (NPDSCH) in a downlink subframe on a carrier, wherein thedownlink subframe immediately follows an uplink subframe, wherein, basedon the carrier being in an in-band mode, the NPDSCH is received startingfrom k^(th) (k>1) orthogonal frequency division multiplexing (OFDM)symbol, without skipping any part of the NPDSCH, and wherein, based onthe carrier being in a guard-band or stand-alone mode, the NPDSCH isreceived, with skipping a starting part of the NPDSCH.
 9. The UEaccording to claim 8, wherein the UE includes a narrowband Internet ofthings (NB-IoT) UE.
 10. The UE according to claim 8, wherein, based onthe carrier being in the guard-band or stand-alone mode, the receptionof the NPDSCH is skipped in at least part of 1^(st) OFDM symbol of thedownlink subframe.
 11. The UE according to claim 10, wherein, based onthe carrier being in the guard-band or stand-alone mode, the NPDSCH isplaced starting from 1^(st) OFDM symbol of the downlink subframe. 12.The UE according to claim 8, wherein the NPDSCH is received, withoutskipping any part of the NPDSCH, further based on two hybrid automaticrepeat request (HARQ) processes being configured.
 13. The UE accordingto claim 8, wherein a subcarrier spacing used for the NPDSCH is 15 kHz.14. The UE according to claim 8, wherein the wireless communicationsystem includes a 3rd party partnership project (3GPP)-based wirelesscommunication system.